1. Technical Field
The present application relates generally to a mobile communications system and, in particular, to a device and method for encoding transmission data to achieve frequency diversity.
2. Description of the Related Art
Generally, in a mobile communications system, voice or data is subject to channel encoding for radio transmission and reception. On a forward link, for example, voice or data to be transmitted is channel-encoded and modulated using modulation techniques such as QPSK (Quadrature Phase Shift Keying). Channel encoding is generally performed for data transmission in a single frequency, and encoded symbols are BPSK (Binary Phase Slift Keying)/QPSK modulated prior to transmission. If a plurality of frequencies and phase channels are available to a user for high-speed data transmission, however, there is a need for assigning transmission data symbols to the plurality of channels.
Conventionally, data symbols are distributed to a plurality of channels for transmission. Advantageously, this method enables optimal data transmission capacity for each channel, but has limitations in recovering data due to possible channel failure or loss of transmission data. The lost data may be recovered by reinforcing data encoding, but with a decrease in transmission efficiency on multiple channels. In addition, when a channel is or remains defective, the channel is either not used or less frequently used until it is recovered. Therefore, communication service quality becomes poor beyond remedy.
These problems can be solved by transmitting the same data on a plurality of frequencies and phase channels. Despite possible failures in some of channels, the data transmitted on the other channels are safe, thereby providing a reliable communication link. Unfortunately, this method significantly decreases channel use efficiency. In particular, since channel encoding and assignment of frequencies and phase channels are independently performed in the conventional technology, it is impossible to consider channel use efficiency when performing data encoding.